Lucy Davis, best known for roles in British television series The Office, and films including 'Shaun of the Dead', 'Wonder Woman' and 'Chilling Adventures of Sabrina', shared the news in a lengthy Instagram post.
The 53-year-old actor said the cancer had spread to her bones, including her spine, right hip and ribs, and that it was too late for chemotherapy.
She said the first sign was not an obvious lump, but a very small hard spot that she almost decided not to have checked.
Davis also said she is not afraid of what comes next and feels at peace with her situation but acknowledged that the prospect of her death is harder for her family than it is for her, saying that any grieving is “for my family”.
The actor said she still hopes to continue working, describing acting as one of the biggest joys in her life.